Ever since I started using the PXS Mail Form plugin in favor of WP-ContactForm for my contact page, I always had problems with it conflicting with the Markdown plugin. Namely, that it disabled the Markdown formatting, and left me with a pile of rubbish.

At the time I decided to keep Markdown and disabled PXS Mail Form, and my contact page took a vacation, but I finally managed to take some time to look a little deeper. Turns out, it’s pretty obvious. Lines 467 through 472:

remove_filter('the_content', 'Markdown', 6);
[... snipped some ...]
add_filter('the_content', 'pxs_callback', 1);

D’oh. In case that doesn’t make sense to you, it’s actually taking the Markdown() filter off and putting its own as priority 1. That’s not good. I ended up changing it to:

//remove_filter('the_content', 'Markdown', 6);
[... snipped some ...]
add_filter('the_content', 'pxs_callback', 14);

So now the line removing Markdown() is commented out, and I lowered (so to speak) the priority of pxs_callback() to 14, and it all works great. Just in case someone else runs into this.